Gradually it has become customary, especially in connection with recovery of hydrocarbons, to use various equipment and components being introduced into a well in order to improve the course of recovery in some way. Such downhole well equipment may comprise various measuring apparatuses, actuators, displacable or rotatable sleeves or valve devices, pumping equipment, etc. The present invention, however, does not depend on the type of downhole equipment used in this connection.
Oftentimes said well equipment requires one or several lines to be extended to surface in order to connect the equipment in the well to corresponding equipment on surface. Typically, such lines are used for energy transmission, fluid transmission and signal communication. As such, the lines may comprise optical-fibre or electric cables/lines for transmission of energy or signals, for example control signals and well data. They may also comprise fluid transmission lines/pipes, for example hydraulic lines, coiled tubings or similar, for transmission of energy, control signals and various well treatment fluids. Thus, the present line includes different types of transmission means of different shape and/or material type, and of more or less flexible design.
During said tripping of the well string, at least one such line will be connected to the well string. When running into the well, the line(s) is/are continuously connected to the well string. When pulling out of the well, the line(s) is/are continuously disconnected from the well string. Under both circumstances, the non-connected portion of such a line is spooled off and onto, respectively, a corresponding spooling unit placed at the well's surface or in the vicinity thereof, for example standing on a drilling floor or being suspended from a winch above the wellbore. Normally, such a spooling unit is large and heavy.
During the tripping operation, however, unforeseen events may occur and give rise to the well string unintentionally being dropped or lowered far too fast into the wellbore. By so doing, the line(s) connected to the well string will also accompany the well string in its uncontrolled trip into the wellbore. This will cause the line(s) to be be spooled out in an uncontrolled manner from a spooling unit nearby. In a worst case scenario in a deep well, the well string and the line(s) may drop several thousands of metres. Such an uncontrolled unspooling may cause uncontrolled movement of both the spooling unit(s) and the line(s), which brings about great danger both to personnel and equipment located in the vicinity of this uncontrolled event. Should the line(s) also become torn off in this connection, a fishing operation must be initiated in the well in order to retrieve both the well string and the line(s), which is time-consuming and costly.
On the basis of dangers and disadvantages associated with such an uncontrolled unspooling of one or several line(s), it would therefore prove very advantageous for the the line(s) to be cut off as soon as possible, and in a safe manner for personnel and quipment. Such an endeavour offers the possibility of limiting the harmful effects of the uncontrolled unspooling.